"The Carnegie Stages of Early Human Embryonic Development: Chart of all 23 Stages, Detailed Descriptions of Stages 1 - 6"

Dianne N. Irving
Copyright April 22, 2006
Reproduced with Permission

Part One: Introduction

In response to an increased awareness of and need and requests for solid and reliable documented information about the international Carnegie Stages of Early Human Embryonic Development and the international nomenclature in human embryology, I am providing that information here so that anyone can find it in the library, on the internet, or buy it from scientific book stores themselves. It is not a big "mystery".

It goes without saying that the stakes involved in insisting on using the accurate scientific facts of human embryology are high. The accurate scientific facts - much of which have been well-known, documented and published for over a hundred years - have been mutilated over the last few decades by those interested in promoting abortion, the use of abortifacients, IVF, prenatal genetic diagnosis, human embryo research, human cloning, human embryonic stem cell research, human genetic engineering, drug and biological/chemical testing and development, etc. Indeed, extensive and influential national and international public policies have already been grounded in such scientific "mis-information". [See Irving, "The impact of scientific 'misinformation' on other fields: Philosophy, theology, biomedical ethics and public policy", Accountability in Research April 1993, 2(4):243-272, at: http://www.all.org/abac/dni009.htm; "When does a human being [normally] begin? 'Scientific' myths and scientific facts", International Journal of Sociology and Social Policy (Feb. 1999), 19:3/4:22-47, at: http://isacco.emeraldinsight.com/vl=8997774/cl=38/nw=1/rpsv/cgibin/linker?ini=emerald&reqidx=/cw/mcb/0144333x/v19n3/s4/p22 (subscription), http://www.l4l.org/library/mythfact.html, and http://www.lifeissues.net/writers/irv/irv_01lifebegin1.html; "What Human Embryo? Funniest Mental Gymnastics from Medicine and Research" (Oct. 14, 2004), at: http://www.lifeissues.net/writers/irv/irv_82whathumanembryo1.html.]

Most people by now are more aware of the accurate human embryology, and should find the following international documentation relatively easy to read. The Carnegie Chart standardizes the well-known scientific facts of human embryology during the "embryonic period", which begins at the beginning of fertilization through slightly more than 8 full weeks post-fertilization. It is composed of 23 Stages of the development of the early human being. Of special note especially see the formal definition of Stage One - as this stage begins when the sperm penetrates the oocyte, and continues until just before the zygote begins its first cleavage division at syngamy. Most human cloning and human genetic engineering takes place during this earliest of Stages of the developing human being, even before the formation of the zygote. Note too the formal definition of "syngamy" as that point during the process of fertilization just before the zygote divides (rather than at the penetration of the oocyte by the sperm). Additionally, observe that the early human embryo divides and multiplies "asynchronously" (not "synchronously"), forming 3-, 5-, 7-cell embryos, etc., as well as 2-, 4- 8-cell embryos, etc.. [E.g., see Stage Two below which references the following: "3 cells, Carnegie No. 8500.1; Described by Menkin and Rock (1948). 5-12 cells, Pathological specimens of 5 (No. 8630), 8 (No. 8450), 9 (No. 8190), and 11 or 12 (No. 8452) cells, found by Hertig et al. (1954). 7 cells, Illustrated by Avendaño et al. (1975)."] Finally, note the accurate scientific facts concerning "implantation". Several stated facts within the text I have bolded (without discussion) to flag them as pertinent to some of the false science used in arguments to "justify" the above stated abortion, IVF and research goals. All graphs, photos and charts (except the Carnegie Chart and Table 1) are not included, but may be fully accessed at the URLs provided. Any typing errors are mine alone.

The Carnegie Stages of Early Human Development is the basis for the Nomina Embryologica which was part of the larger Nomina Anatomica for decades until 1989. In 1999 the name was changed by the International Associations of Anatomists to Terminologia Embryologica and Terminologia Anatomica, which was published in 1999 by the International Federation of Associations of Anatomists (IFAA) and is available for sale in book or CD-Rom format at: http://www.thieme.com/SID2194056226451/productsubpages/pubid-1163116455.html.

For on-line access to information about the international Nomina Embryologica Committee and the Carnegie Stages of Early Human Development, see the U.S. national websites at the National Museum of Health and Medicine, Armed Forces Institute of Pathology:

The following recommended internationally recognized human embryology textbooks are, as professionally required, in concert with the Carnegie Stages and the international nomenclature on human embryology and include the full Chart of the Carnegie Stages in their texts:

Discussions in these texts about the Carnegie Stages includes the following:

Ronan O'Rahilly and Fabiola Muller, Human Embryology & Teratology (New York: Wiley-Liss, 2001): "In preparing this book, the authors have made full use of the [Carnegie Embryological] Collection and of the various published studies, whether by themselves or by others, based on what George W. Corner felicitously termed that 'Bureau of Standards'.... Serious work in human embryology now depends on staging and the internationally accepted system of Carnegie embryonic stages (a term introduced by the senior author) has been adopted throughout.... A scheme of embryonic stages can be found on the inside front cover of this book. These developmental stages are indicated by superscripts throughout this book, thereby avoiding interruptions in the flow of the text." (p. ix)

Ibid, O'Rahilly and Muller (1994): "Wilhelm His, Senior (1831-1904), the founder of human embryology [Fig. 1-1].... [H]uman embryology is scarcely more than one hundred years old. The first to study the human embryo systematically was Wilhelm His, Senior, who established the basis of reconstruction, i.e., the assembling of three-dimensional form from microscopic sections. His, who has been called the 'Vesalium of human embryology,' published his three-volume masterpiece Anatomie menschlicher Embryonen in 1880-85 [His, Vogel, Leipzig]. In it the human embryo was studied as a whole for the first time.... A detailed Handbook of Human Embryology by Keibel and Mall appeared in 1910-12. Franklin P. Mall, who studied under His, established the Carnegie Embryological Collection in Baltimore and was the first person to stage human embryos (in 1914). Mall's collection soon became the most important repository of human embryos in the world and has ever since served as a 'Bureau of Standards'. Mall's successor, George L. Streeter, laid down the basis of the currently used staging system for human embryos (1942-48), which was completed by O'Rahilly (1973) and revised by O'Rahilly and Muller (1987)." (p. 3)

Keith Moore and T. V. N. Persaud, The Developing Human: Clinically Oriented Embryology (6th ed. only) (Philadelphia: W. B. Saunders Company, 1998): "Schleiden and Schwann were responsible for great advances being made in embryology when they formulated the cell theory in 1839. This concept stated that the body is composed of cells and cell products. The cell theory soon led to the realization that the embryo developed from a single cell, the zygote, which underwent many cell divisions as the tissues and organs formed." (p. 12)

For more information on the historical development of these international scientific standards, see, e.g., article on Wilhelm Hiss, at: http://www.whonamedit.com/doctor.cfm/2606.html.

The Carnegie Collection is housed at the National Museum of Health and Medicine [http://nmhm.washingtondc.museum], in Washington, D.C. In their "Collections" section one can find the following description of the Carnegie Collection: [http://nmhm.washingtondc.museum/collections/hdac/index.htm]:

"The Carnegie Stages of Early Human Development are posted on the website of The Human Developmental Anatomy Center (HDAC), part of the Research Collections division of the National Museum of Health & Medicine, acquires and maintains collections pertaining to general developmental anatomy and neuroanatomy.... Collections such as the ones housed at the Human Developmental Anatomy Center provide researchers a central location from which to obtain data about normal development for both human and common research species. HDAC maintains and archives the largest collection of human and comparative developmental material in the United States, in such a way as to make them most useful for research activities, yet preserve them for future generations of researchers. Access to the HDAC collections is available to any researcher or student. Those requesting access to the collections can email a preliminary request to the Center or phone 202-782-2682."

Part Two: No "Pre-Embryo", No "Pre-Embryo Substitutes", No "Biogenetics Law"

Upon reading and understanding the accurate scientific facts of human embryology fully documented in these long-recognized international standards in professional sources, it becomes quite obvious that if the new genetically unique living human embryo, the individual human being/organism, begins to exist at the beginning of Stage One then there is no such thing as a "pre-embryo" or any similarly concocted "pre-embryo substitute" that supposedly exists after fertilization - even though these false scientific terms are still in use in some legislation, regulations, etc. In fact, the international nomenclature committee has specifically rejected as unscientific the terms "individualization", "pre-embryo" and thus any similar "pre-embryo substitutes". As succinctly put by O'Rahilly and Muller:

"The term 'pre-embryo' is not used here for the following reasons: (1) it is ill-defined because it is said to end with the appearance of the primitive streak or to include neurulation; (2) it is inaccurate because purely embryonic cells can already be distinguished after a few days, as can also the embryonic (not pre-embryonic!) disc; (3) it is unjustified because the accepted meaning of the word embryo includes all of the first 8 weeks; (4) it is equivocal because it may convey the erroneous idea that a new human organism is formed at only some considerable time after fertilization; and (5) it was introduced in 1986 'largely for public policy reasons' (Biggers).... Just as postnatal age begins at birth, prenatal age begins at fertilization." (O'Rahilly and Muller 2001, p. 88) ... The ill-defined and inaccurate term pre-embryo, which includes the embryonic disc, is said either to end with the appearance of the primitive streak or to include neurulation. The term is not used in this book.. (O'Rahilly and Muller 1994, p. 55)... The term conception, however, may refer either to fertilization or to implantation and hence (like gestation) is best avoided." (O'Rahilly and Muller 2001, p. 19).

Likewise, the old now-defunct but still used "Biogenetic Law" is also grossly scientifically inaccurate and rejected:

"Recapitulation, the So-Called Biogenetic Law. The theory that successive stages of individual development (ontogeny) correspond with ('recapitulate') successive adult ancestors in the line of evolutionary descent (phylogeny) became popular in the nineteenth century as the so-called biogenetic law. This theory of recapitulation, however, has had a regrettable influence on the progress of embryology (G. de Beer).... According to the 'laws' of von Baer, general characters (e.g., brain, notochord) appear in development earlier than special characters (e.g., limbs, hair). Furthermore, during its development an animal departs more and more from the form of other animals. Indeed, the early stages in the development of an animal are not like the adult stages of other forms but resemble only the early stages of those animals. The pharyngeal clefts of vertebrate embryos, for example, are neither gills nor slits. Although a fish elaborates this region into gill slits, in reptiles, birds, and mammals it is converted into such structures as the tonsils and the thymus." (O'Rahilly and Muller 2001, p. 16)

However, such scientific information is obviously "helpful" when used to insert legal loopholes into laws and regulations (among other things).

Part Three: Full Carnegie Chart of 23 Stages of Early Human Embryonic Development:


Human Developmental Anatomy Center

Table 1
Development Stages in Human Embryoes
Below is a table of the 23 Carnegie stages of development and their major descriptive features. Quoting directly, with the exception of the "Age" titles which I have interpreted according to the data as "post" either fertilization or ovulation.
Carnegie Stage Pairs of Somites Length
1 1 Fertilization
2 1.5-3 2-3 From 2 to about 16 cells
3 4 4-5 Free blasocyst
4 5-6 5-6 Attaching blastocyst
5 0.1-0.2 7-12 7-12 Implanted although previllous
5a 0.1 7-8 Solid trophoblast
5b 0.1 9 Trophoblastic lacunae
5c 0.15-0.2 11-12 Lacunar vascular circle
6 0.2 13 13-15 Chorionic villi; primitive streak may appear
6a Chorionic villi
6b Primitive streak
7 0.4 16 15-17 Notochordal process
8 1.0-1.5 18 17-19 Primitive pit, notochordal and neurenteric canals
9 1.2-2.5 20 19-21 Somites first appear
10 2-3.5 22 22-23 Neural folds begin to fuse, 2
pharyngeal bars, optic sulcus
11 2.5-4.5 24 23-26 Rostral neuropore closes, optic vesicle
12 3-5 26 26-30 Caudal neuropore closes, 3 pharyngeal
bars, upper limb buds appearing
13 4-6 28 28-32 Four limb buds, lens disc, otic vesicle
14 5-7 32 31-35 Lens pit and optic cup, endolymphatic
appendage distinct
15 7-9 33 35-38 Lens vesicle, nasal pit, antitragus
beginning, hand plate, trunk relatively wider,
cerebral vesicles
16 8-11 37 37-42 Nasal pit faces ventrally, retinal pigment
visible in intact embryo, auricular
hillocks beginning, foot plate
17 11-14 41 42-44 Head relatively larger, trunk straighter,
nasofrontal groove distinct, auricular hillocks
distinct, finger rays
18 13-17 44 44-48 Body more cuboidal, elbow region and toe
rays appearing, cyclids beginning, tip of nose
distinct, nipples appear, ossification may
19 16-18 47.5 48-51 Trunk elongating and straightening
20 18-22 50.5 51-53 Upper limbs longer and bent at elbows
21 22-24 52 53-54 Fingers longer, hands approach each other,
feet likewise
22 23-28 54 54-56 Eyelids and external ear more
23 27-31 56.5 56-60 Head more rounded, limbs longer and more

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